Resin Composition

The present invention relates to a resin composition which shows especially excellent balance of mechanical properties including mainly rigidity and is superior in processability, oil resistance and chemical resistance.

More particularly, it relates to a resin composition for injection molding, extrusion molding or blow molding which comprises a polyolefin, especially, a crystalline polyolefin, a polyphenylene ether resin, a partially hydrogenated alkenyl aromatic compound-isoprene block copolymer and an alkenyl aromatic compound-conjugated diene block copolymer and is excellent in balance of mechanical properties of mainly rigidity and heat resistance and superior in processability, organic solvent resistance and chemical resistance.

Polyolefins are superior in processability, toughness, water resistance, organic solvent resistance, chemical resistance, etc., low in specific gravity and inexpensive and hence have been widely used for production of various shaped articles and sheets. However, they suffer from the problem in heat resistance, which has hindered development of new uses thereof.

On the other hand, polyphenylene ether resins have excellent heat resistance, but has difficulties in processability and solvent resistance, which impose limitation on the scope of application. For improvement polyphenylene ether resin with a styrene resin is utilized, but this has defect in solvent resistance and is limited in scope of application. For example, the blend is not suitable in the field which requires resistance to oily solvents such as gasoline.

In an attempt to utilize the respective merits of these polyolefin and polyphenylene ether and offset their defects, various blend compositions have been proposed. For example, a composition has been proposed for improvement of processability and tensile strength (Japanese Patent Kokoku No. 42-7069). However, this composition does not necessarily suffice the relatively high level of mechanical strength which is required in industrial fields. Furthermore, for improving compatibility between polyolefin and polyphenylene ether resin to enhance mechanical strength, for example, a composition to which a styrene-butadiene block copolymer or its hydrogenated product is added (Japanese Patent Kokai Nos. 53-71158, 54-88960 and 59-100159) and the above composition to which inorganic filler is added (Japanese Patent Kokai No. 58-103556) have been proposed. According to these proposals, processability and mechanical strength can be improved, but the organic solvent resistance possessed by polyolefin cannot be sufficiently exhibited for the reasons that amount of polyolefin added is small or matrix (continuous phase) comprises polyphenylene ether resin or combination of polyphenylene ether resin and styrene resin and the like. Moreover, there has been proposed a composition which comprises polyphenylene ether and a large amount (more than 20% by weight) of polyolefin to which are further added a diblock copolymer or radial teleblock copolymer composed of alkenyl aromatic compound and conjugated diene or hydrogenated polymers thereof as a compatibilizing agent (Japanese Patent Kokai Nos. 58-103557 and 60-76547. That is, it is said that a blend of a-low density polyethylene as polyolefin and polyphenylene ether resin has been improved in compatibility and can be improved in tensile characteristics and fragility by the addition of hydrogenated product of alkenyl aromatic compound - conjugated diene block copolymer. However, improvement only in compatibility is not enough to satisfy various properties required for common resins. For example, the composition disclosed in Japanese Patent Kokai No. 60-76547 a resin composition comprising the three components of a polyphenylene ether, a low-density polyethylene as polyolefin, a component of large amount, and a hydrogenated product of alkenyl aromatic compound-conjugated diene block copolymer as a compatibilizing agent for the former two components has limitation in its use owing to its very low rigidity level. Among the above-mentioned combinations, resin compositions which contain polypropylene as polyolefin are somewhat improved in rigidity and heat resistance, but these are still not enough in practical use and further improvement has been desired.

The inventors have conducted intensive research in an attempt to make further improvement and to provide resin compositions which can satisfy balance of mechanical strength of relatively high level and solvent resistance and processability of relatively high level which are required in various uses such as fields of industrial parts.

As a result of investigation conducted by the inventors on polyphenylene ether resin, polyolefin and various additives, it has been found that a resin composition which shows excellent balance of mechanical properties and is superior in solvent resistance and processability can be obtained by adding a hydrogenated product of an alkenyl aromatic compound-conjugated diene block copolymer of a specific structure and an alkenyl aromatic compound-conjugated diene block copolymer to combination of polyphenylene ether resin and polyolefin, preferably crystalline polyolefin. Thus, the present invention has been accomplished.

The present invention is a resin composition which comprises:

(a) a polyolefin resin in an amount of 20-95% by weight,

(b) a polyphenylene ether resin in an amount of 80-5% by weight,

(c) a partially hydrogenated alkenyl aromatic compound-isoprene block copolymer in an amount of 2-45 parts by weight based on totally 100 parts by weight of the components (a) and (b), and

(d) an alkenyl aromatic compound-conjugated diene block copolymer in an amount of 3-45 parts by weight based on totally 100 parts by weight of the components (a) and (b).

Component (a) : Polyolefin resin

Polyolefins used in the present invention include, for example, homopolymers of .alpha.-olefins of 3 or more carbon atoms such as propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, heptene-1, and octene-1, copolymers of predominant amount of these .alpha.-olefins and .alpha.-olefin containing ethylene in the form of random copolymer, block copolymer and the like and mixtures thereof, copolymers such as random, block, and graft copolymers of a predominant amount of .alpha.-olefins of 3 or more carbon atoms and other unsaturated monomers, and oxidized, halogenated or sulfonated products of these polymers. Preferred are those which are at least partially crystalline.

As the other unsaturated monomers, there may be used unsaturated organic acids or derivatives thereof such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, maleic anhydride, arylmaleic acid imide, and alkylmaleic acid imide; vinyl esters such as vinyl acetate and vinyl butyrate; aromatic vinyl compounds such as styrene and methylstyrene; vinyl silanes such as vinyltrimethylmethoxysilane and methacryloyloxypropyltrimethoxysilane; and non-conjugated dienes such as dicyclopentadiene, 4-ethylidene-2-norbornene, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene.

In case of copolymers, these may comprise not only two of .alpha.-olefins or other monomers, but also more than two of them.

These polymers can be obtained by polymerization or modification according to known processes and besides, commercially available polymers may be optionally chosen and used. Combination of them can naturally be employed.

Among them, preferred are homopolymers of propylene, butene-1,3-methylbutene-1 or 4-methylpentene-1 and copolymers containing a predominant amount of these monomers. Among them, crystalline propylene polymers, namely, crystalline propylene homopolymer, crystalline propylene-ethylene block or random copolymer, and mixtures of these crystalline propylene polymers with .alpha.-olefin rubbers, namely, rubber-like copolymers comprising a plurality of .alpha.-olefins or rubber-like copolymers of a plurality of .alpha.-olefins and non-conjugated dienes are especially preferred from the point of balance in mechanical properties.

Melt flow rate (MFR) (230.degree. C., load 2.16 kg) of these crystalline propylene polymers and mixtures containing these crystalline propylene polymers and .alpha.-olefin rubbers is preferably within the range of 0.01-400, more preferably within the range of 0.15-60. If MFR is less than 0.01, the composition often has 10 problems in processability and if it is more than 400, level of mechanical strength is low and this is not preferred.

Polyolefins include those which have come to have an MFR within the above range by allowing polyolefins having smaller MFR, namely, larger molecular weight to undergo change in molecular weight according to known method, for example, heat treatment in the presence or absence of free-radical initiator (organic or inorganic peroxides, organotin compounds, organic azo compounds, etc.) or heating and mechanical shearing at melt kneading.

Component (b) : Polyphenylene ether resin

The polyphenylene ether resin used in the present invention has a recurring unit represented by the following formula: ##STR1## wherein the ether oxygen atom in one unit links to benzene nucleus in the next adjacent unit; n is at least 30; a plurality of R each represents a monovalent substituent selected from the group consisting of hydrogen, halogen, hydrocarbon group containing no tertiary-carbon atom, halohydrocarbon group having at least two carbon atoms between halogen atom and phenyl nucleus, hydrocarbon oxy group and halohydrocarbon oxy group having at least two carbon atoms between halogen atom and phenyl nucleus.

Typical examples of polyphenylene ethers are the following and analogues thereof.

Poly(2,6-dimethyl-1,4-phenylene) ether,

Poly(2,6-diethyl-1,4-phenylene) ether,

Poly(2-methyl-6-ethyl-1,4-phenylene) ether,

Poly(2-methyl-6-propyl-1,4-phenylene) ether,

Poly(2,6-dipropyl-1,4-phenylene) ether,

Poly(2-ethyl-6-propyl-1,4-phenylene) ether,

Poly(2,6-dibutyl-1,4-phenylene) ether,

Poly(2,6-dipropenyl-1,4-phenylene) ether,

Poly(2,6-dilauryl-1,4-phenylene) ether,

Poly(2,6-diphenyl-1,4-phenylene) ether,

Poly(2,6-diethoxy-1,4-phenylene) ether,

Poly(2-methoxy-6-ethoxy-1,4-phenylene) ether,

Poly(2-ethyl-6-stearyloxy-1,4-phenylene) ether,

Poly(2,6-dichloro-1,4-phenylene) ehter,

Poly(2-methyl-6-phenyl-1,4-phenylene) ether,

Poly(2,6-dibenzyl-1,4-phenylene) ether,

Poly(2-ethoxy-1,4-phenylene) ether,

Poly(2-chloro-1,4-phenylene) ether,

Poly(2,5-dibromo-1,4-phenylene) ether.

Further examples are copolymers such as copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol, copolymer of 2,6-dimethylphenol and 2,3,5,6-tetramethyl-phenol and copolymer of 2,6-diethylphenol and 2,3,6-trimethylphenol.

The polyphenylene ethers used in the present invention further include modified polyphenylene ethers such as polyphenylene ethers defined by the above-mentioned formula on which a styrene monomer (e.g., styrene, p-methylstyrene, and o-methylstyrene) is grafted.

Processes for preparation of these polyphenylene ethers have been known as disclosed, for example, in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,257,357, and 3,257358, Japanese Patent Kokoku No. 52-17880 and Japanese Patent Kokai No. 50-51197.

Polyphenylene ethers preferred for attaining the objects of the present invention are those which have alkyl substituents in the two ortho positions in respect to the ether oxygen atom and copolymers of 2,6-dialkylphenol and 2,3,6-trialkylphenol.

Among them, polymers of 2,6-dimethylphenol are especially preferred. Further, molecular weight of the polyphenylene ethers in terms of intrinsic viscosity measured in chloroform at 25.degree. C. is preferably within the range of 0.2-0.7 dl/g, more preferably within the range of 0.25-0.6 dl/g and further preferably within the range of 0.3-0.55 dl/g. If the intrinsic viscosity is less than 0.2 dl/g, mechanical strength of composition is insufficient and if more than 0.7 dl/g, processability of the composition is deteriorated.

Furthermore, polyphenylene ethers may be replaced with styrene resins such as polystyrene, high-impact polystyrene reinforced with various rubbers and ABS resin in an amount of less than half of the weight of polyphenylene ethers.

Component (c) : Partially hydrogenated alkenyl aromatic compound-isoprene copolymer:

The partially hydrogenated alkenyl aromatic compound-isoprene block copolymer used in the present invention is an alkenyl aromatic compound-isoprene block copolymer which has a structure containing at least one chain block "A" originating from the alkenyl aromatic compound and at least one chain block "B" originating from the isoprene and in which content of aliphatic unsaturated group in the block B is reduced by hydrogenation. Arrangment of block A and block B includes linear structure and branched structure, so-called radial teleblock structure.

Distribution of monomer components is not critical and may be uniform or ununiform and furthermore may be tapered with increase or decrease in the amount of monomer components along molecular chain. Therefore, respective molecular weight of block A and block B may be the same or different. Moreover, a part of these structures may contain random chain originating from random copolymer portion of alkenyl aromatic compound and isoprene. Among them, preferred are linear structures such as diblock (A-B blocks), triblock (A-B-A blocks, B-A-B blocks), tetrablock (A-B-A-B blocks), pentablock (A-B-A-B-A blocks, B-A-B-A-B blocks) and those which have totally 6 or more A and B blocks. More preferred are diblock, triblock and tetrablock structures and A-B diblock structure is especially preferred.

The alkenyl aromatic compound which constitutes block A has the chemical structure represented by the following formula. ##STR2## wherein R.sup.1 and R.sup.2 each represents hydrogen atom or a lower alkyl or alkenyl group of 1-6 carbon atoms, R.sup.3 and R.sup.4 each represents a hydrogen atom, a lower alkyl group of 1-6 carbon atoms, a chlorine atom or a bromine atom, and R.sup.5, R.sup.6 and R.sup.7 each represents a hydrogen atom or a lower alkyl or alkenyl group of 1-6 carbon atoms and R.sup.6 and R.sup.7 may link together with a hydrocarbyl group to form a naphthyl group.

Examples of the alkenyl aromatic compounds include styrene, p-methylstyrene, .alpha.-methylstyrene, vinylxylene, vinyltoluene, vinylnaphthalene, divinylbenzene, bromostyrene and chlorostyrene and these may also be used in combination. Among them, styrene, .alpha.-methylstyrene, p-methylstyrene, vinyltoluene, and vinylxylene are preferred and styrene is more preferred.

Proportion of the recurring unit originating from alkenyl aromatic compound in the partially hydrogenated alkenyl aromatic compound-isoprene block copolymer (c) is preferably more than 20% by weight and at most 80% by weight, more preferably 25-65% by weight, more preferably 25-65% by weight. If the proportion is more than 80% by weight, impact strength of resin composition is deteriorated to unsatisfactory level and if it is 20% by weight or less, rigidity level and heat resistance of resin composition are insufficient and the objects of the present invention cannot be attained.

In the aliphatic chain portion of the block copolymer (c), proportion of unsaturated bond remaining without being hydrogenated is preferably 50% by weight or less, more preferably 20% by weight or less, further preferably 10% by weight or less. Further, about 25% by weight or less of aromatic unsaturated bond originating from alkenyl aromatic compound may be hydrogenated.

The hydrogenated block copolymer (c) has a number-average molecular weight (obtained according to polystyrene conversion method from values measured by gel permeation chromatography) of preferably 5,000-500,000 g/mol, more preferably 10,000-300,000 g/mol, still further preferably 30,000-200,000, especially 45,000-150,000 g/mol. If the number-average molecular weight is more than 500,000 g/mol or less than 5,000 g/mol, production cost is apt to increase.

Measurement by gel permeation chromatography was carried out by using monodispersed polystyrene as standard material in obtaining relation between elution time and molecular weight. The average molecular weight was in terms of polystyrene.

Molecular weight distribution of the hydrogenated block copolymer (c) can be measured by the above gel permeation chromatography, but preferred molecular weight distribution is not limited and besides so-called value Q obtained by dividing value of weight-average molecular weight by that of number-average molecular weight may be within any range. Moreover, the molecular weight distribution may have not only one peak, but also two or more peaks. Moreover, the block copolymer (c) may be such that containing, in addition to the component of peak of main dispersion, a small amount of components of higher or lower molecular weight than that of the component of the peak of main dispersion, in other words, having shape of molecular weight distribution comprising a peak of main dispersion having the foot descending by a gradual slope.

The alkenyl aromatic chain block (block A) and the hydrogenated isoprene chain block (block B) in the hydrogenated block copolymer (c) may be of any molecular weight as far as it satisfies the above-mentioned number-average molecular weight and may be of any combinations.

These hydrogenated block copolymers (c) have hydrogenated isoprene polymer chain portion and some of them show crystallinity originating from this chain. It is considered that this is because the hydrogenated isoprene polymer chain has a molecular structure similar to polyolefin. Crystallinity of the hydrogenated block copolymer (c) can be measured by differential scanning calorimeter (DSC).

The hydrogenated block copolymers (c) usable in the present invention may be of any crystallinity.

The hydrogenated block copolymers (c) may have any glass transition temperatures based on the hydrogenated isoprene polymer chain portion.

The glass transition temperature can be measured by the above-mentioned DSC method or based on change of viscoelasticity with temperature measured by mechanical spectrometer or the like.

Many processes have been proposed for producing alkenyl aromatic compound-isoprene block copolymers. Typical processes are disclosed, for example, in Japanese Patent Kokoku No. 40-23798, U.S. Pat. Nos. 3,595,942 and 4,090,996. According to these processes, block copolymerization is carried out in an inert solvent such as cyclohexane using lithium catalyst, Ziegler catalyst or the like. One of these block copolymers is supplied from Japan Synthetic Rubber Co., Ltd. by the trademark of "TR2400". Hydrogenation treatment of these block copolymers is carried out by 5 hydrogenation in an inert solvent such as cyclohexane in the presence of hydrogenation catalyst according to the processes disclosed in Japanese Patent Kokoku Nos. 42-8704, 43-6636 and 46-20814.

As compounds similar to the partially hydrogenated alkenyl aromatic compound-isoprene block copolymer, there are known partially hydrogenated alkenyl aromatic compound-butadiene block copolymers, specifically, hydrogenated styrene-butadiene block copolymers. However, when these copolymers are used, compatibility 5 between polyolefin resin and polyphenylene ether resin is somewhat insufficient and besides, heat resistance such as heat distortion temperature is considerably inferior and the objects of the present invention cannot be attained.

Component (d) : Alkenyl aromatic compound-conjugated diene block copolymer

The alkenyl aromatic compound-conjugated diene block copolymer used in the present invention is a block copolymer having a structure having at least one chain block "A" originating from the alkenyl aromatic compound and at least one chain block "B" originating from the conjugated diene. Arrangement of block A and block B includes linear structure and branched structure, namely, a so-called radial tele block structure. Furthermore, it may contain random chain originating from random copolymer portion of alkenyl aromatic compound and conjugated diene in a part of these structures.

These block copolymers are usually those which have a structure represented by the following formulas: A-B, A-(B-A).sub.n-1, (A-B).sub.n X, (A-B-A).sub.n X (wherein X represents a residue of a coupler having at least two functional groups and n represents an integer of 2 or more). Total amount of block A contained in such block copolymer is 10-80% by weight, preferably 20-60% by weight.

Content of alkenyl aromatic compound in block A is preferably at least 60% by weight, more preferably 80% by weight, especially preferably 100% by weight and content of alkenyl aromatic compound in block B is preferably 40% by weight or less, more preferably 30% by weight or less. When component of small amount is present in respective blocks, its distribution in molecular chain may be any of random, tapered, partially block-like distribution or combination thereof. When number of respective polymer blocks is two or more, these may be the same or different structure.

Number-average molecular weight of block A or block B is preferably 1,000-300,000, more preferably 5,000-100,000. Number-average molecular weight of the whole block copolymer is preferably 10,000-500,000, more preferably 20,000-300,000. Molecular weight distribution is preferably 1.01-10.

The alkenyl aromatic compound which constitutes the block copolymer is the same as the alkenyl aromatic compound mentioned in the item of component (c) and styrene is preferred.

Examples of the conjugated diene compound is butadiene, isoprene and 1,3-pentadiene.

These block copolymers may further be modified with unsaturated carboxylic acids or derivatives thereof. Examples of these unsaturated carboxylic acids or derivatives thereof are maleic acid, fumaric acid, acrylic acid, methacrylic acid, chloromaleic acid, itaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and endo-cis-bicyclo[2,2,1]-5-heptene-2,3-dicarboxylic acid and besides, acid anhydrides, esters, amides and imides of these carboxylic acids. Of these unsaturated carboxylic acids or derivatives thereof, preferred are maleic acid, fumaric acid, maleic anhydride and glycidyl methacrylate.

The block copolymers are obtained usually by anion polymerizing a vinyl aromatic compound and a conjugated diene compound in an inert hydrocarbon solvent such as benzene, hexane or cyclohexane using an organolithium compound such as butyllithium as a polymerization catalyst. Besides, the block copolymers having a lithium activated terminal which are obtained by this process can be coupled with a polyfunctional coupler such as silicon tetrachloride to obtain branched or radial block copolymers. The block copolymers may be an aromatic vinyl compound-conjugated diene block copolymer, prepared by any other processes.

Content of polyolefin, component (a), in the resin composition of the present invention is preferably 20-95% by weight, more preferably 30-95% by weight, especially preferably 50-90% by weight when total amount of polyolefin (a) and polyphenylene ether resin (b) is assumed to be 100% by weight.

If the content is less than 20% by weight, composition is insufficient in organic solvent resistance and if it is more than 95% by weight, heat resistance is in unsatisfactory level and the object of the present invention cannot be attained.

Similarly, content of polyphenylene ether resin, component (b), is preferably 80-5% by weight, more preferably 70-5% by weight and especially preferably 50-10% by weight when total amount of component (a) and component (b) is assumed to be 100% by weight. If it is less than 5% by weight, level of rigidity is insufficient and if it is more than 80% by weight, organic solvent resistance is insufficient.

Content of the partially hydrogenated alkenyl aromatic compound-isoprene block copolymer, the component (c), is preferably 2-45 parts by weight, more preferably 3-20% parts by weight, especially preferably 3-10 parts by weight based on totally 100 parts by weight of component (a) and component (b). If it is less than 2 parts by weight, level of impact strength is unsatisfactory and if it is more than 45 parts by weight, level of rigidity is unsatisfactory and the object of the present invention cannot be attained.

Content of the alkenyl aromatic compound-conjugated diene block copolymer, component (d), is preferably 3-45 parts by weight, more preferably 5-30 parts by weight based on totally 100 parts by weight of component (a) and component (b). If it is less than 3 parts by weight, level of impact strength is insufficient and if it is more than 45 parts by weight, level of rigidity is unsatisfactory and the object of the present invention cannot be attained.

The resin composition of the present invention may contain, in addition to the above components, auxiliary components as far as the effects of the present invention are not damaged. Examples of these components are antioxidant, weathering modifier, nucleating agent for polyolefin, slip agent, inorganic or organic fillers and reinforcing agent, flame retardant, various colorants, antistatic agent, releasing agent, and a small amount of free-radical initiator (organic peroxides, etc.) for molecular weight regulation of polyolefins.

Furthermore, plasticizer such as triphenyl phosphate used for polyphenylene resin, and furthermore, fillers such as glass fiber, wollastonite, potassium titanate, whisker, mica, talc, and calcium carbonate are effective for improvement of balance of properties such as rigidity and improvement of processability, dimensional accuracy, and dimensional stability.

As method of blending for obtaining the resin composition of the present invention, various methods can be employed which are generally used for blending of resins per se; resins and stabilizer or colorant; resins and filler; and the like. For example, respective components in the form of powder or particle are made into a homogeneously dispersed mixture by Henschel mixer, super mixer, ribbon blender, V blender, etc. Then, the mixture is melt kneaded by twin-screw extruder, single-screw extruder, roll, Banbury mixer, blast mill, melt kneader with Brabender Plastograph, etc. Melt kneading temperature is usually 200.degree.-350.degree. C. The thus obtained resin composition can be extruded into pellets after melt kneading.

The resin composition of the present invention can be easily molded by molding methods generally applied to thermoplastic resins, namely, injection molding, extrusion molding, blow molding, etc., among which injection molding is most preferred. Because of its good mechanical properties, the composition is suitable for automobile parts, specifically, exterior trim parts such as bumper, door, door panel, fender, ornament, emblem, wheel cover, engine hood, roof, and spoiler, internal trim parts such as instrument panel, console box, and trim, exterior parts of electrical equipments such as television, refrigerator, and so-called office automation equipments.

The present invention will be explained by the following nonlimiting examples and comparative examples.

In the following Examples and Comparative Examples, properties were measured and evaluated under the following conditions.

(1) MFR (for indication of flowability)

MFR of polyolefin was measured according to JIS K 7210-1975.

(2) Flexural modulus (for indication of rigidity)

This was measured in accordance with ISO R 178-1974 Procedure 12 (JIS K 7203) using Instron tester.

(3) Izod impact strength

This was measured in accordance with ISO R 180-1969 (JIS K 7110) (notched Izod impact strength) using Izod impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd.

(4) Heat distortion temperature (for indication of heat resistance

This was measured in accordance with ISO R 75-1958 Method A (JIS K 7207- 1974 A) using an injection molded test piece subjected to annealing treatment at 100.degree. C. for 30 minutes.

A propylene homopolymer [SUMITOMO NOBRENE D-501 (trademark) manufactured by Sumitomo Chemical Co. Ltd.], poly-(2,6-dimethylphenylene) ether (manufactured by Sumitomo Chemical Co., Ltd.), a hydrogenated styrene-isoprene block copolymer (hereinafter referred to as "hydrogenated SI") [KRATON G1701X (trademark) manufactured by Shell Chemical Co.], and a styrene-butadiene block copolymer [CALIFLEX TR-1101 (trademark) manufactured by Shell Chemical Co.] were mixed at a mixing ratio as shown in Table 1 by a super mixer. The resulting mixture was melted kneaded by a twin-screw extruder [TEM-50 (trademark) manufactured by Toshiba Machine Co., Ltd.] at 260.degree.-280.degree. C. to obtain pellets. Properties of test piece made therefrom were measured and the results are shown in Table 1.

In the same manner as in Example 1, pellets were prepared from a composition of proplylene homopolymer, poly-(2,6-dimethylphenylene) ether and hydrogenated styrene-isoprene block copolymer and measurement of properties was conducted. The results are shown in Table 1.

As is clear from comparison of the results of Example 1 with those of Comparative Example 1, the composition obtained from only polypropylene, poly-(2,6-dimethylphenylene) ether and hydrogenated styreneisoprene block copolymer is low in both the heat distortion temperature and flexural modulus and the composition of the present invention is excellent in balance of properties.

Pellets were prepared in the same manner as in Example 1 except that a hydrogenated styrene-butadiene block copolymer (hereinafter referred to as "hydrogenated SB") was used in place of the hydrogenated styrene-isoprene block copolymer. Measurement of properties was conducted to obtain the results as shown in Table 1.

As can be seen from comparison of the results of Example 1 with those of Comparative Example 2, when hydrogenated styrene-butadiene block copolymer which was silimar to the hydrogenated styrene-isoprene block copolymer was used in place of the latter, the resulting composition is low in all of heat distortion temperature, flexural modulus and impact strength while the composition of the present invention is excellent.

Pellets were prepared in the same manner as in Example 1 at a mixing ratio of the components as shown in Table 2 and properties were evaluated. The results are shown in Table 2. Components used in Table 2 are as follows:

Homopolymer: SUMITOMO NOBRENE D-501 (trademark) manufactured by Sumitomo Chemical Co., Ltd.

Block copolymer: Propylene-ethylene block copolymer [SUMITOMO NOBRENE AS-171A (trademark) manufactured by Sumitomo Chemical Co., Ltd.,]

Random copolymer: Propylene-ethylene random copolymer [SUMITOMO NOBRENE S-131 (trademark) manufactured by Sumitomo Chemical Co., Ltd.]

Polyphenylene ether: Poly-(2,6-dimethylphenylene) ether manufactured by Sumitomo Chemical Co., Ltd.]

Hydrogenated SI: KRATON G-1701X (trademark) manufactured by Shell Chemical Co.

CALIFLEX TR-1101 (trademark) manufactured by Shell Chemical Co.

As explained above, the resin composition of the present invention shows excellent balance of mechanical strength and is good in solvent resistance and processability.

The resin composition can be easily processed into shaped articles by molding methods applied to general thermoplastic resin compositions such as injection molding, extrusion molding and blow molding. The resulting articles are very good in balance of properties such as impact resistance, heat resistance and solvent resistance and are excellent in uniformity and smoothness of surface.